Dynamic load-sharing power system

ABSTRACT

A power system is provided for a marine or petroleum drilling vessel. The power system may have a plurality of power sources, at least one power consumer, and an input device configured to generate a signal indicative of a desired output. The power system may also have a load manager associated with the at least one power consumer and configured to create a power demand for the plurality of power sources based on the signal and an actual output, and a controller. The controller may be configured to determine a plurality of performance goals for the plurality of power sources, determine a priority of the performance goals, retrieve from the plurality of power sources at least one performance map corresponding with each performance goal, and selectively apportion the power demand between of each of the plurality of power sources based on the at least one performance map and based on the determined priority.

TECHNICAL FIELD

The present disclosure relates generally to a power system and, more particularly, to a dynamic load-sharing power system.

BACKGROUND

Marine vessels often include multiple engines harnessed together to drive one or more primary loads (e.g., propellers) and various auxiliary loads (e.g., HVAC, lighting, pumps, etc.). The engines can be mechanically connected to the loads or electrically connected to the loads by way of generators. In some applications, the loads of a vessel can be driven both mechanically and electrically in a hybrid arrangement.

In typical marine applications, all engines are simultaneously operated to produce about the same amount of power. For example, a particular marine vessel may have four identical engines each capable of producing about 5,000 kW. And during operation, all of the engines may be operated at the same level (e.g., at about 20% capacity) to evenly distribute the loads (e.g., to evenly distribute a 4,000 kW load). In some situations, however, an even distribution of the loads between the engines may not optimal. For instance, operating four engines at 20% capacity may be less fuel efficient, less responsive, and/or produce more emissions than operating only one of the engines at about 80% capacity or operating two engines at 30% capacity and one engine at 20% capacity.

An attempt at improving power generation efficiency is disclosed in U.S. Patent Application Publication 2013/0342020 of Blevins et al, that published on Dec. 26, 2013 (“the '020 publication”). In particular, the '020 publication discloses a power grid having a set of controllable generators and a grid controller. The grid controller is configured to provide a load partition configuration for the set of generators that achieves a total fuel consumption goal, a response time goal, or a stability goal. The load partition is determined from performance characterization models that are developed based on performance curves provided by the generator manufacturer, maintenance data, monitored performance data, and environmental data.

Although touted as an improvement over existing technologies, the power grid of the '020 publication may still be less than optimal. In particular, the performance curves of the different generators may not be publically available or maintained. That is, manufacturers of the generators may not be willing to publish the necessary and proprietary performance curves for use by a third party competitor. And developing the curves based on measured data may be time consuming, expensive, and inaccurate. Further, the power grid of the '020 publication may only be applicable to stationary power grids having static operating conditions (e.g., operators, applications, environmental conditions, etc.). And finally, it may be possible for performance goals to change based on changing operations of the power grid, and the power grid of the '020 publication does not provide a way to accommodate this type of change.

The disclosed power system is directed to improvements over existing systems.

SUMMARY

According to one exemplary aspect, the present disclosure is directed to a power system. The power system may include a plurality of power sources, at least one power consumer driven by the plurality of power sources, and an input device configured to generate a signal indicative of a desired output of the at least one power consumer. The power system may also include a load manager associated with the at least one power consumer and configured to create a power demand for the plurality of power sources based on the signal and an actual output of the power consumer, and a controller in communication with the load manager and the plurality of power sources. The controller may be configured to determine a plurality of performance goals for the plurality of power sources, determine a priority of the plurality of performance goals, retrieve from each of the plurality of power sources a performance map corresponding with each of the plurality of performance goals, and selectively apportion the power demand between of each of the plurality of power sources based on the performance map and based on the determined priority.

According to another exemplary aspect, the present disclosure is directed to a control network for a power system having a plurality of engines, a plurality of generators driven by the plurality of engines, and at least one electrical load driven by the plurality of generators. The control network may include a load manager configured to receive input from an operator of the power system indicative of a desired output of the at least one electrical load and to responsively create a power demand for the plurality of generators based on the input and an actual output of the at least one electrical load. The control network may also include an engine controller associated with each of the plurality of engines, and a power system controller in communication with the load manager and the engine controller of each of the plurality of engines. The power system controller may be configured to determine at least one performance goal for the plurality of engines associated with at least one of fuel consumption, emissions, and transient response; and retrieve from the engine controller of each of the plurality of engines a performance map corresponding with the at least one performance goal. The power system controller may also be configured to selectively apportion the power demand unequally between of each of the plurality of engines based on the performance map and based on the priority.

According to yet another exemplary aspect, the present disclosure is directed to a method of controlling a power system. The method may include operating a plurality of engines to power a propeller and auxiliary loads of a marine vessel, receiving a signal indicative of a desired output of the propeller and the auxiliary loads, and creating a power demand for the plurality of engines based on the signal and an actual power output. The method may also include determining a plurality of performance goals for the plurality of engines associated with at least one of fuel consumption, emissions, and transient response; prioritizing the plurality of performance goals; retrieving from each of the plurality of engines a performance map corresponding to the plurality of performance goals; and selectively apportioning the power output unequally between of each of the plurality of engines based on the performance map and a priority of the plurality of performance goals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric illustration of an exemplary disclosed machine;

FIG. 2 is an diagrammatic illustration of an exemplary disclosed power system that may be used in conjunction with the machine of FIG. 1; and

FIG. 3 is a flowchart depicting an exemplary disclosed method of operating the power system of FIG. 2.

DETAILED DESCRIPTION

FIG. 1 illustrates a marine vessel (“vessel”) 10 having a power system 12 configured to supply power to one or more consumers or loads 14. Power system 12 may be anchored to a platform 16 within a hull 18 of vessel 10, and at least partially controlled from a bridge 20 (or another location onboard and/or offboard vessel 10). Loads 14 may include any device or devices that consume mechanical and/or electrical power, including, but not limited to, motors (not shown) that drive propellers of vessel 10 and electric lights, HVAC systems, water pumps, and other auxiliary loads that are normally found on a conventional marine vessel.

FIG. 2 illustrates power system 12 during three different operations, including a Pulling operation, a Deep Dynamic Positioning (DDP) operation, and a Port operation. As can be seen in FIG. 2, power system 12 may include, among other things, a plurality of power sources 22, a load manager 24, and a power system controller 26. Power sources 22 may create a mechanical and/or electrical power output. Load manager 24 may determine a power demand for power sources 22 based on input received from bridge 20 and on an actual output or performance of loads 14. Power system controller 26 may selectively adjust operation of power sources 22 in different ways to meet the demand from load manager 24.

Power sources 22 may embody any number and type of combustion engines, some or all of which that are connected to corresponding generators to form generator sets. The mechanical outputs of the combustion engines may be routed directly to loads 14 (e.g., mechanically routed to the propellers) and/or indirectly by way of the generators (e.g., electrically routed to motors of the propellers and to the other auxiliary loads). In the disclosed embodiment, power system 12 includes four different power sources 22, including two pairs of substantially identical generator sets. These pairs include two larger medium-speed generator sets and two smaller high-speed generator sets. The larger medium-speed generator sets may be capable of greater power output at higher fuel efficiency (i.e., lower fuel consumption) and/or lower emissions. The smaller high-speed generator sets, however, may be capable of faster transient response and high-efficiency low-load operation. By including a mix of different types and/or sizes of generator sets, benefits associated with the different sets may be realized. It is contemplated, however, that a particular vessel 10 could include identical generator sets, all different generator sets, or any other configuration of generator sets, as desired. It is also contemplated that power sources other than engines and generators may be used to power vessel 10, for example batteries or other power storage devices.

Load manager 24 may be configured to compare an actual output of power system 12 to a desired output (e.g., desired travel speed, desired propeller speed, desired vessel location, etc.), and create a power demand based on the difference. In the disclosed example, load manager 24 is a generator controller configured to compare an actual bus voltage to a desired voltage and responsively generate a command for electrical power supply based on the difference. In the example of FIG. 2, the propellers of vessel 10 are electrically powered from a common bus and directly controlled from bridge 20. In this example, the captain of vessel 10 (or another operator) may move a throttle lever (not shown) to command vessel 10 (and/or a particular propeller) to move at a particular desired speed. As signals from bridge 20 cause the propellers to turn on, turn faster, slow down, or turn off, the motors associated with the propellers may consume more or less electricity from the common power bus. This change in power consumption may cause a corresponding voltage fluctuation in the bus, and load manager 24 may monitor the voltage fluctuation and responsively generate the command for more or less electrical power to be supplied by the generator sets to the bus.

In another example, load manager 24 may be a stand-alone component and configured to compare an actual vessel travel speed or actual propeller speed to a desired travel or desired propeller speed and generate a command for a change in power (mechanical and/or electrical) based on the difference. In yet another example, load manager may compare an actual vessel position and/or orientation to a desired position or orientation, and generate a command for a change in power based on the difference. Other comparisons may also be instituted by load manager 24, and load manager 24 may take any conventional configuration known in the art for creating the power demand. Signals generated by load manager 24 indicative of the power demand may be directed to controller 26 for further processing.

Controller 26 may include commonly known components that cooperate to apportion the power demand from load manager 24 among the different power sources 22. Controller 26 may include, among other things, a single or multiple microprocessors, digital signal processors (DSPs), etc. that include means for controlling an operation of power system 12. Numerous commercially available microprocessors can be configured to perform the functions of controller 26. It should be appreciated that controller 26 could readily embody a microprocessor separate from that controlling other vessel- or engine-related functions, or that controller 26 could be integral with a vessel microprocessor and be capable of controlling numerous functions and modes of operation. As a separate microprocessor, controller 26 may communicate with the general vessel microprocessor(s) and/or engine controllers via datalinks or other methods. Various other known circuits may be associated with controller 26, including power supply circuitry, signal-conditioning circuitry, actuator driver circuitry (i.e., circuitry powering solenoids, motors, or piezo actuators), and communication circuitry.

Controller 26 may apportion a given power demand from load manager 24 unequally between the different power sources 22 based on different performance goals. For example, controller 26 may apportion the power demand a first way when the performance goal is to reduce fuel consumption (Brake Specific Fuel Consumption—BSFC), a second way when the performance goal is to provide high transient response, a third way when the performance goal is to produce low emissions, and a fourth way when the performance goal is reduce wear of power sources 22. For instance, for a given power demand from load manager 24, controller 26 may command the larger medium-speed generator sets to satisfy more of the demand when the performance goal is low fuel consumption and/or low emissions. But for the same demand, controller 26 may command the smaller medium-speed generator sets to satisfy more of the demand when the performance goal is associated with transient response or wear.

In the exemplary embodiment, the performance goals may be manually selected or automatically determined based on a current operation of vessel 10. Specifically, the captain of vessel 10 may be able to select via one or more input devices (not shown) located within bridge 20 whether fuel consumption, transient response, emissions, wear or another performance characteristic should be established as a goal for use in power demand apportioning. Alternatively, the current operation of vessel 10 (Pulling, DDP, Port) may correspond with one or more particular performance goals.

In some applications, multiple performance goals may be simultaneously used to apportion the power demand from load manager 24 between the different power sources 22. In these applications, the performance goals may be prioritized, and the priority of the goals used by controller 26 to weight apportioning of the power demand. For example, the captain may select low fuel consumption as the first priority performance goal, low emissions as the second, and high transient response as the third. And based on this priority of performance goals, controller 26 may apportion the power demand differently when compared to a different priority. Similarly, different operations of vessel 10 may correspond with a different set of prioritized goals. For example, DDP operations may correspond with high transient response as the first goal, then low fuel consumption, then low emission; Pulling operations may correspond with low fuel consumption as the first goal, then high transient response, then low emission; and Port operations may correspond with low emissions as the first goal, then low fuel consumption, then high transient response.

Controller 26 may apportion the power demand from load manager 24 based on the priority of the performance goals and based on different control maps associated with each power source 22. Specifically, controller 26 may retrieve from each power source 22 (e.g., from a control unit associated with each engine and/or with each generator) at least one map associated with the performance goals. For example, controller 26 may retrieve a fuel consumption map, an emissions map, a transient response map, a wear map, and/or any other map known in the art. These maps may normally be used by the different power source controllers to regulate fueling (e.g., start of injection timing, injection duration, injection pressure, injection amount, end of injection timing, number of injection pulses, etc.) of the different engines and/or field spacing of the different generators at a given engine speed. Controller 26, however, may utilize these maps to determine a combined performance of all power sources 26 at different possible apportionment configurations and to then select a particular configuration that achieves the selected goal(s). It is contemplated that the maps may be different for each power source and/or for each different type of power source, as needed.

For example, when the selected performance goal is low fuel consumption, controller 26 may retrieve a fuel consumption map from the engine controller of each power source 22. Controller 26 may then compare different apportionments of the power demand from load manager 24 with the fuel consumption map to determine the particular configuration of apportionments that provides the overall lowest fuel consumption possible from all of the power sources 22. In some embodiments, this may result in an equal apportionment of the power demand between the different power sources 22. In most instances, however, the apportionment may be unequal. In fact, in some instances, one or more of the power sources 22 may be operated to satisfy a majority of the power demand and one or more others of the other power sources 22 may supply little of the demand or even be turned off.

When multiple performance goals are simultaneously selected (manually by the captain or automatically based on vessel operations), controller 26 may retrieve multiple performance maps from the engine controllers. Controller 26 may then reference the different maps with weightings based on a priority of the selected goals. In some embodiments, controller 26 may overlap the maps or otherwise create collective 3-D maps (see FIG. 2) that relate parameters associated with the different performance goals. Controller 26 may then reference the priority weightings with the collective maps to determine the apportionments that satisfy the power demand in a manner based on the priority of the selected goals. For example, controller 26 may use the priority weightings as scale factors when apportioning the power demand. It may be possible that, when multiple goals are selected, the outcome of the first performance goal may not be the best possible outcome, as the outcome of the second and third performance goals may have some affect on the outcome of the first performance goal.

In some applications, it may be possible over time for performance of a particular power source 22 to drift away from the control maps stored within the corresponding engine controllers. For example, it may be possible for an older engine to have decreased performance due to wear, or for system inputs (e.g., fuel quality, wind current, ocean current, ambient air temperature, etc.) to deviate from assumed or expected values. In these situations, controller 26 may be capable of modifying the existing control maps based on monitored engine performance. Specifically, controller 26 may be capable of monitoring, processing, and recording engine performance for future use in power demand apportioning.

Controller 26 may rely on different sensors when monitoring engine performance and/or modifying the existing control maps. These sensors may include, for example, one or more fuel flow meters associated with each engine, speed sensors, torque sensors, emission sensors (e.g., NOx sensors), temperature sensors, pressure sensors, voltage sensors, current sensors, fuel level sensors, DEF (diesel exhaust fluid) level sensors. DEF flow meters, and other performance sensors. Controller 26 may also be capable of computing different aspects of engine and/or generator performance based on measured parameters. For example, controller 26 may be capable of computing engine torque, emissions, and/or wear based on measured rpm, fuel flow rates, temperatures, and/or pressures. Controller 26 may then update and/or create the required control maps based directly on the measured parameters and/or based on the calculated parameters. It is contemplated that controller 26 may only determine performance drift away from the control maps based on the measured/calculated parameters, and then allow the captain of vessel 10 to selectively implement or ignore accommodations for the drift, as desired.

In some applications, controller 26 may also selectively apportion the power demand between the different power sources 22 based on a desired power reserve. Specifically, the captain of vessel 10 may desire a particular amount of power be left in reserve from particular power sources 22, and this power reserve may limit the way in which controller 26 can apportion the power demand.

Similarly, controller 26 may take environmental factors into consideration when apportioning the power demand between power sources 22. For example, controller 26 may consider wind currents, water currents, GPS location of vessel 10 (e.g., within port or away from port), vessel traffic (e.g., number of other vessels in the immediate area based on radar information), and selectively direct particular power sources 22 to satisfy a greater or smaller portion of the power demand based on these factors.

FIG. 3 is a flow chart depicting an exemplary operation of power system 12. FIG. 3 will be discussed in the following section to further illustrate the disclosed system and its operation.

INDUSTRIAL APPLICABILITY

The disclosed power system may be applicable to any mobile machine having multiple power sources. However, the disclosed power system may be primarily applicable to a marine and/or petroleum drilling vessel application, where the power sources cooperate to propel the vessel and to power auxiliary loads under varying conditions. The disclosed power system may allow for enhanced performance through optimization of select goals in a priority that is manually selected by the captain of the vessel or automatically selected based on a current operation of the vessel. Operation of power system 12 will now be described in detail.

As shown in FIG. 3, operation of power system 12 may begin with controller 26 receiving a power demand from load manager 24 (Step 300). The power demand may be based on, for example, a reduction in voltage on a common bus providing power to one or more loads 14 (e.g., to propellers and an HVAC system) of vessel 10. In response to the reduction in voltage, load manager 24 may call for an increased power out, for example an output of about 10,500 kW. In this example, power system 12 may be capable of outputting about 15,000 kW with four power sources 22 (i.e., with two larger medium-speed generator sets at 5,000 kW each, and two smaller high-speed generator sets at 2,500 kW each).

At about the same time, controller 26 may determine a current operation of vessel 10, a list of prioritized performance goals, and/or a desired power reserve (Step 310). The current operation may be manually input by the captain of vessel 10 and/or automatically determined by controller 26 based on any number of different parameters (e.g., based on current location, current speed, current maneuvering, etc.). In one example, the current operation may be one of a DDP operation, a Pulling operation, and a Port operation. During the DDP operation, vessel 10 is away from port and its position is being automatically maintained through the use of the propellers based on signals from reference sensors, wind sensors, current sensors, motion sensors, compass sensors, etc. During the Pulling operation, vessel 10 is away from port and traveling toward a destination. During the Port operation, the vessel is stationary or moving at slow speed under regulated conditions within a port setting. The list of prioritized goals and desired power reserve may likewise be manually received or automatically determined. Specifically, the captain of vessel 10 may manually select from a list of available goals in an order of priority and also stipulate the desired power reserve. Alternatively, the prioritized goals and power reserve may be linked to the current operation of vessel 10.

After receiving the power demand from load manager 24 and after determining the current operation, the prioritized list of goals, and the desired power reserve, controller 26 may obtain (i.e., retrieve and/or develop) the associated performance maps (Step 320). As discussed above, controller 26 may retrieve the same performance maps from the controllers (i.e., from the engine and/or generator controllers) of power sources 22 that are normally used to regulate operation (e.g., fueling, boost, etc.) of the associated engines and/or generators. These maps may include fuel consumption maps, emissions maps, transient response maps, wear maps, and any other maps known in the art. And when these maps are no longer accurate, controller 26 may develop and update the maps based on monitored performance.

Controller 26 may then apportion the power demand received from load manager 24 among power sources 22 based on the retrieved maps and in a way that achieves the prioritized goals and maintains the desired power reserve (Step 330). For example, when the current operation is determined to be Pulling (either based on manual input or automatically based on monitored vessel performance), controller 26 may determine that the list of prioritized goals should be low fuel consumption, then high transient response, then low emissions. And for this prioritization and based on the power demand of 10,500 kW, controller 26 may apportion the power demand as shown in the upper example of FIG. 2. In particular, controller 26 may distribute the power demand between only one of the smaller high-speed gensets and both of the larger medium-speed gensets. This apportionment may call for the smaller high-speed genset to operate at about 20% of its capacity, and both of the larger medium-speed gensets to operate at about 100% of their capacities. This would leave a combined power reserve in the smaller high-speed gensets of about 4,500 kW.

If the current operation was instead a DDP operation, the power demand would likely be less than it would be for a Pulling operation, and controller 26 may determine that the list of prioritized goals should be high transient response, then low fuel consumption, then low emission. And for this prioritization, controller 26 may alternatively apportion the lower power demand among the different power sources 22 as shown in the middle example of FIG. 2. Specifically, this apportionment may call for the smaller high-speed gensets to provide a greater amount of the power demand. For example, the smaller high-speed gensets may operate at about 50% of their capacities, and only one of the larger medium-speed gensets may operate at about 100% of its capacity for a total of about 7,500 kW of power. This would leave a power reserve in the remaining larger medium-speed genset and in the smaller high-speed gensets of about 7,500 kW.

If the current operation was instead a Port operation, the power demand would also likely be less than it would be for a Pulling operation, and controller 26 may determine that the list of prioritized goals should be low emission, then low fuel consumption, then high transient response. And for this prioritization, controller 26 may alternatively apportion the power demand among the different power sources 22 as shown in the lower example of FIG. 2. Specifically, this apportionment may call for the smaller high-speed gensets to operate at about 85% and 30% of their capacity, respectively, and for one of the larger medium-speed gensets to operate at about 100% of its capacity for a total of about 7,875 kW of power. This would leave a power reserve in the remaining larger medium-speed genset and in the smaller high-speed gensets of about 7,125 kW.

After determining the appropriate apportionment of the power demand among the available power sources 22, controller 26 may then command corresponding operation of the power sources 22, and cause the selected apportionment configuration to be displayed within bridge 20 (Step 340). By displaying the apportionment configuration within bridge 20, the captain may have the opportunity to adjust and/or override the configuration, if desired.

Many advantages may be associated with power system 12. For example, because controller 26 may retrieve the performance maps directly from power sources 22, it may be likely that the maps are maintained and contain all of the information necessary to properly operate power sources 22. In other words, the power source 22 may not be required to operate on only publically available information. Further, power system 22 may allow for multiple performance goals to be selected and simultaneously improved upon in different ways depending on a priority of the goals. In addition, power system 22 may allow for changing operations, environmental conditions, captains, etc. to have an effect on the way in which power demands are apportioned. For these reasons, power system 22 may have enhanced applicability to many different situations.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed power system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed power system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

What is claimed is:
 1. A power system, comprising: a plurality of power sources; at least one power consumer driven by the plurality of power sources; an input device configured to generate a signal indicative of a desired output of the at least one power consumer; a load manager associated with the at least one power consumer and configured to create a power demand for the plurality of power sources based on the signal and an actual output of the power consumer; and a controller in communication with the load manager and the plurality of power sources, the controller being configured to: determine a plurality of performance goals for the plurality of power sources; determine a priority of the plurality of performance goals; retrieve from each of the plurality of power sources at least one performance map corresponding with each of the plurality of performance goals; and selectively apportion the power demand between of each of the plurality of power sources based on the at least one performance map and based on the determined priority.
 2. The power system of claim 1, wherein the plurality of power sources includes a plurality of engines.
 3. The power system of claim 2, wherein at least one of the plurality of power sources further includes a generator mechanically driven by one of the plurality of engines.
 4. The power system of claim 2, wherein the plurality of engines includes engines having different output capabilities.
 5. The power system of claim 2, wherein the at least one power consumer includes at least one of a propeller of a marine vessel and auxiliary loads of the marine vessel.
 6. The power system of claim 2, wherein the plurality of performance goals are associated with transient response, fuel consumption, emissions, and engine wear.
 7. The power system of claim 6, wherein the priority is operator selectable.
 8. The power system of claim 6, wherein: the power system is associated with a marine vessel; and the priority is automatically selected based on a current operation of the marine vessel.
 9. The power system of claim 8, wherein: the current operation is one of a deep dynamic positioning operation, a pulling operation, and a port operation; and the plurality of performance goals include low fuel consumption, high transient response, and low emissions.
 10. The power system of claim 9, wherein: when the current operation is a deep dynamic positioning operation, the priority of the plurality of performance goals includes high transient response, then fuel consumption, then emissions; when the current operation is a pulling operation, the priority of the plurality of performance goals is low fuel consumption, then transient response, then emissions; and when the current operation is a port operation, the priority of the plurality of performance goals is low emissions, then fuel consumption, then transient response.
 11. The power system of claim 9, wherein each different operation has a different power demand apportionment between the plurality of power sources.
 12. The power system of claim 1, wherein the controller is configured to selectively apportion the power demand based further on monitored performances of the plurality of power sources.
 13. The power system of claim 12, wherein the monitored performances include at least one of fuel flow, rpm, torque, inlet manifold air pressure, and inlet manifold air temperature.
 14. The power system of claim 1, wherein the controller is further configured to selectively apportion the power demand based further on a desired power reserve.
 15. The power system of claim 1, further including a display located within an operator station, wherein the controller is further configured to show on the display how the power demand is apportioned.
 16. The power system of claim 1, wherein: the power system is associated with a marine vessel; and the controller is configured to selectively apportion the power demand based also on wind and water currents affecting the marine vessel.
 17. The power system of claim 1, wherein the controller is further configured to: determine performance drift of the plurality of power sources away from the at least one performance map; and selectively allow apportionment of the power demand based on the performance drift.
 18. The power system of claim 1, wherein the controller is configured to apportion the power demand unequally between the plurality of power sources.
 19. A control network for a power system having a plurality of engines, a plurality of generators driven by the plurality of engines, and at least one electrical load driven by the plurality of generators, the control network comprising: a load manager configured to receive input from an operator of the power system indicative of a desired output of the at least one electrical load and to responsively create a power demand for the plurality of generators based on the input and an actual output of the at least one electrical load; an engine controller associated with each of the plurality of engines; and a power system controller in communication with the load manager and the engine controller of each of the plurality of engines, the power system controller configured to: determine at least one performance goal for the plurality of engines associated with at least one of fuel consumption, emissions, and transient response; retrieve from each of the engine controllers of each of the plurality of engines a performance map corresponding with the performance goal; determine a priority for the at least one performance goal; and selectively apportion the power demand unequally between of each of the plurality of engines based on the performance map and based on the determined priority.
 20. A method of controlling a power system, comprising: operating a plurality of engines to power a propeller and auxiliary loads of a marine vessel; receiving a signal indicative of a desired output of the propeller and the auxiliary loads; creating a power demand for the plurality of engines based on the signal and an actual power output of the propeller and auxiliary loads; determining a plurality of performance goals for the plurality of engines associated with at least one of fuel consumption, emissions, and transient response; prioritizing the plurality of performance goals; retrieving from each of the plurality of engines at least one performance map corresponding to the plurality of performance goals; and selectively apportioning the power demand unequally between of each of the plurality of engines based on the at least one performance map and a priority of the plurality of performance goals. 